Wireless charging is a method of running an electric current through electromagnetic induction to thereby charge up a battery, and for this, a magnetic field generated in a first coil of a charging panel is induced to a second coil connected to the battery to thereby supply the electric current. Such a wireless charging is usefully applied to portable communication apparatuses, electric vehicles, and so on, which require charging of mass storage batteries, has little danger of an electrical short because contact points are not exposed, and can prevent a bad connection of a wire connector type.
A short-distance electromagnetic induction charging method is to transmit electric power converted into electromagnetism between a wireless transmitting panel of a power supply and a wireless receiving panel of a target apparatus to be charged. The shorter a distance between the wireless transmitting panel and the wireless receiving panel, the more an electric energy is concentrated, so that electricity of high efficiency can be transmitted to the target apparatus to be charged in safety. Such technology has been used in various apparatuses for more than 100 years, and can charge batteries as fast as and as safe as the wire charging method according to using methods. Moreover, the technology does not cause confusion with other apparatuses around the target apparatus due to the short-distance electromagnetic induction, is easy to use because of the wireless charging method, is environmental-friendly by minimizing waste of energy, and enables manufacturing of reliable products, which are strong to dust and moisture.
In the meantime, recently, wireless electricity transmission technology has been improved to the level to transmit electricity to electronic products, which are about 30 cm apart to the maximum, and if the transmission distance is expanded to 10 meters in the future, it is expected that the applicable fields is widened to Televisions, home appliances, automobiles, robots, and so on. Wireless power transmission is a power transmitting method of a new concept to transmit energy by converting an electric energy into microwaves, which is favorable to wireless transmission, has the principle of radio wave transmission to send the electric energy through a space without electric wires. Furthermore, the wireless power transmission is not the concept of transmit signals used in the wireless communication systems, such as radios, wireless telephones, and so on, but the concept of transmit electric energy. In other words, the general wireless communication is to send signals with carrier signals, but the wireless power transmission is to send only carrier waves.
Recently, with the introduction of electric vehicles, an attention to construction of the charging infrastructure is increasing. Charging methods of various kinds, such as replacement of batteries, high-speed charging devices, wireless charging devices, and others including the method of charging electric vehicles using chargers for home use, have been disclosed, and new business models for charging business are also appearing now. Electric vehicles and charging stations which are in trial run start to attract people's attention in Europe, and in Japan, automobile manufacturers and electric power companies lead a trial run of electric vehicles and charging stations.
Because it is expected that electric vehicles will become popular in the future, safe and high-speed charging methods to reduce a charging period of time and increase convenience are required, and hence, non-contact wireless charging methods of various types to solve inconvenience in wire charging methods that a plug is put in a socket have been proposed.
The general short-distance wireless charging method has an advantage in that it is safe because a plug is not directed put a socket, but has a problem in that its transmission efficiency is remarkably reduced when the corresponding electromagnetic induction panels are spaced too far apart. Accordingly, in order to charge a high-capacity battery loaded in an electric vehicle, it is necessary to innovatively improve the wireless charging devices, which are low in transmission efficiency and require a lot of time to charge the battery.